/* ------------------------------------------------------------------------
 *
 * geqo_px.cpp
 *
 *	 position crossover [PX] routines;
 *	 PX operator according to Syswerda
 *	 (The Genetic Algorithms Handbook, L Davis, ed)
 *
 * IDENTIFICATION
 * src/gausskernel/optimizer/geqo/geqo_px.cpp
 *
 * -------------------------------------------------------------------------
 */
/* contributed by:
   =*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
   *  Martin Utesch				 * Institute of Automatic Control	   *
   =							 = University of Mining and Technology =
   *  utesch@aut.tu-freiberg.de  * Freiberg, Germany				   *
   =*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
 */
/* the px algorithm is adopted from Genitor : */
/*************************************************************/
/* 															 */
/* 	Copyright (c) 1990										 */
/* 	Darrell L. Whitley										 */
/* 	Computer Science Department								 */
/* 	Colorado State University								 */
/* 															 */
/* 	Permission is hereby granted to copy all or any part of  */
/* 	this program for free distribution.   The author's name  */
/* 	and this copyright notice must be included in any copy.  */
/* 															 */
/*************************************************************/

#include "postgres.h"
#include "knl/knl_variable.h"
#include "optimizer/geqo_random.h"
#include "optimizer/geqo_recombination.h"

/* px
 *
 *	 position crossover
 */
void px(PlannerInfo* root, Gene* tour1, Gene* tour2, Gene* offspring, int num_gene, City* city_table)
{
    int num_positions;
    int i, pos, tour2_index, offspring_index;

    /* initialize city table */
    for (i = 1; i <= num_gene; i++)
        city_table[i].used = 0;

    /* choose random positions that will be inherited directly from parent */
    num_positions = geqo_randint(root, 2 * num_gene / 3, num_gene / 3);

    /* choose random position */
    for (i = 0; i < num_positions; i++) {
        pos = geqo_randint(root, num_gene - 1, 0);

        offspring[pos] = tour1[pos];          /* transfer cities to child */
        city_table[(int)tour1[pos]].used = 1; /* mark city used */
    }

    tour2_index = 0;
    offspring_index = 0;

    /* px main part */
    while (offspring_index < num_gene) {
        /* next position in offspring filled */
        if (!city_table[(int)tour1[offspring_index]].used) {
            /* next city in tour1 not used */
            if (!city_table[(int)tour2[tour2_index]].used) {
                /* inherit from tour1 */
                offspring[offspring_index] = tour2[tour2_index];
                tour2_index++;
                offspring_index++;
            } else { /* next city in tour2 has been used */
                tour2_index++;
            }
        } else { /* next position in offspring is filled */
            offspring_index++;
        }
    }
}
